A man was stabbed in the neck with a broken bottle at a Jessie J gig in South London last night, The Telegraph reports.

The party was hosted by BlackBerry and was attended by a number of reality TV stars and rappers.

The unnamed man, who was in his 30s, is in a critical condition, and witnesses have said there was a large amount of blood on the floor after the incident. According to some witnesses, the stabbing happened when everyone rushed to leave the venue at the end of the event.

Police have already arrested one man they suspect to be involved in the stabbing.

Police did not allow any more guests to leave the premises until they investigated the area; around 450 people were held at the event until 1:50am.

People who were at the event took to twitter…

@Ed_StarOnSunday: There’s been an incident at the Blackberry party and no one is currently allowed to leave #bbmparty #OMG

@OhmyGOD: someones been stabbed with a broken bottle at the #bbmparty !? That’s awful. How absolutely horrific.

@JRosellenM: So I can’t leave the #BBMparty cos some1 got shanked in the neck #ThisCantBeLife